The Value Of CT And MRI In Diagnosing Annular Pancreas In The Adults

Objective：To assess the value of CT and MRI findings of annularpancreas in the adults which is an uncommon congenital pancreaticanomaly. Summarizing its direct signs and indirect signs in order toimprove the recognition of this disease for radiologists. To compare andanalyze the advantages and disadvantages of CT and MRI in the diagnosisfo annular pancreas in the adults. The ultimate aim of this study was toprovide the basis for clinical to choose the appropriate diagnosis methods.Methods： Six adult patients confirmed annular pancreas wereretrospectively analyzed. Three cases were underwent plain andcontrast-enhanced CT scanning, the other three cases were underwent plainand contrast-enhanced MRI scanning, among of them, one case wasundertaken MRCP examination.The images feature of each cases were evaluated in detail. Theparameters included the anatomical feature of pancreas and duodenum,extension of the pancreatic head, dilation of main pancreatic duct, dilationof common bile duct, dilation of the intrahepatic bile duct, pancreatitis and cholecystitis. CT and MRI findings were reviews by two senior radiologistsblindly, assessed the parameters of all subjects and the consensus of thefinal diagnosis were reached.Results：According to the recent three years situation in our hospital,the morbidity of annular pancreas is approximately0.024per cent. Both CTand MRI findings can detect annular pancreas by visualizing not only thedirect signs but also the indirect signs. The imaging findings of all caseswere extension of pancreatic head which encircled the second portion ofthe duodenum. The other two cases can detect the annular pancreatic duct.The indirect signs included dilation of the intrahepatic bile duct (twocases), the common bile duct (three cases) and the Wirsung duct (fourcases),pancreatitis (one case) and cholecystitis (one case).Plain CT scan showed significant enlarged pancreatic head in all threecases, but was not able to observe the direct signs and make a diagnosis ofannular pancreas. Contrast enhancement in the arterial phase showedpancreatic tissue enhancement was obvious and duodenal tissue was notenhanced, ring of pancreatic tissue encircled the second part of theduodenum completely or partial.Plain MRI scan showed abnormal in both T1WI sequence and T2WIsequence in one case, the images of the other two cases were normal.Contrast enhancement in the arterial phase in T1WI with fat-suppressed sequence, we can detect the high signal intensity of the pancreatic tissueencircling the low signal intensity of the duodenal second portion due tothe signal drop of background adipose tissue. CE-MRI scan can visualizethe direct signs in all three cases.Conclusion： The imaging method of diagnosis annular pancreas inthe adults included CT and MRI. Each of it can reveal the direct signs andindirect signs. findings can detect annular pancreas by visualizing not onlythe direct signs but also the indirect signs. Annular pancreas in the adultsshould be distinguished from duodenal diverticulum. It suggests that bothCE-CT and CE-MRI are a accurate and reliable methods in diagnosis ofannular pancreas in the adults. CE CT scan be a pivotal method indiagnosis of annular pancreas in the adults by demonstrating themorphologic features clearly. CE MRI in combination with MRCP may beshown as more sensitive than CT which is suitable for children and youngpatients, but the average costs is expensive.